A method of this type is known, for example, from DE 10 2007 012 236 A1. First of all, a decoration layer is applied to the surface of a composite wood board which can be subsequently processed further, for example, to produce floor panels or can be used as a furniture board. A sealing varnish layer is applied to the decoration layer and a structure is embossed into the completely hardened varnish layer. The structuring takes place by way of an embossing calender or an intermittently operated press with temperature and pressure loading. Before the application of the decoration layer onto the upper side of the carrier board, a color layer can previously be printed on as carrier layer. The carrier layer can also be composed of paper. The decoration of the decoration layer is preferably a wood or stone reproduction. However, a cork, leather or tile visual appearance can also be produced instead of a wood decoration. As a result of the structure which is embossed into the varnish layer and corresponds, for example, to the grain of the wood decoration or the vein patterns of the stone reproduction, a particularly natural visual appearance of the finished composite wood board is achieved.
EP 1 918 095 A1 has disclosed a composite wood board with a core of wood material, which composite wood board has a real wood veneer layer on its upper side. The surface of the veneer layer is printed with at least one ink application which changes the decoration. The printing takes place in such a way that the decoration of the veneer changes visually to a different real wood decoration. The veneer layer can be printed in an analog and digital manner.
Since the introduction of digital printing in the wood industry, more and more products are finished with the aid of this technology. There are a wide variety of reasons for this. The essential reason for using digital printing consists in the fact that considerably better print quality can be achieved in comparison with analog printing processes (gravure printing). Firstly, higher resolutions can be achieved by way of digital printing and secondly digital printing is not restricted in relation to the possible colors, as is the case, for example, in gravure printing. As a result, new color spaces can be opened up by the use of digital printing, which new color spaces are not accessible by means of a gravure printing process. In analog printing, impression rolls with a circumference of up to approximately 1.4 m are used. However, the composite wood boards can be produced in every desired length, and even in an endless manner. As a result of the limitation of the roll circumferences, the printing motif is then repeated again and again. If the composite wood boards are subsequently divided into individual panels and used, for example, as a floor covering, the result is an artificial decoration image which is always found again at various points in the floor covering as a result of the repetitions of the decoration. The floor covering can be recognized as an “artificial” product. Real wood panels or natural stone tiles do not have a repeating decoration. Each real wood panel/each natural stone tile is provided with an individual decoration, with the result that no floor panel is the same as another. The decoration is distributed randomly over the floor covering.
Decorations which are only repeated after considerably more than 40 m can be realized using digital printing. In principle, decorations which are completely without repetitions are even possible. Considerably greater options are also available to digital printing with regard to the color spaces than in the case of analog printing. In digital printing, composite wood boards can therefore be finished, the decoration of which is distributed randomly and, if composite wood boards of this type are then later processed further to produce floor coverings, a random distribution of the decoration is achieved, as is customary in the case of real wood or natural stone floors.
It is a disadvantage in the use of digital printing, however, that the printing inks are considerably more expensive than the printing inks for gravure printing. For this reason, the production costs of digitally printed composite wood boards lie considerably above those of analog printed boards. In addition, digital printing is slower than gravure printing, which likewise results in high production costs.